Dial test indicators upside down

[digiex-chris]

I learned something important about dial indicators this weekend while dialing in a horizontal bore on my horizontal mill.

http://www.longislandindicator.com/p139.html

"We had a belligerent customer whose dial indicator wasn't returning to zero when he used it upside down. We told him that dial indicators are designed to be used right side up. He said "Bull****," which put us on the defensive. We called one of the major US manufacturers, the one located in Athol, Mass., and asked them. They said, indeed, the dial indicator has to be used right side up, that "gravity is a factor in the equation." If the indicator has to be used inverted, then a much stronger return spring has to be installed.

The literature that comes with the brand new digital indicators from Japan's leading manufacturer states plainly and clearly that their state-of-the-art indicator will work anywhere between upright and horizontal. It says nothing about working between horizontal and upside down. Now we feel vindicated, and that complaining customer can eat his words."

In other words, they work fine vertically and horizontally, but not plunger-up. Probably a compromise so they don't have to manufacture to watch standards for a position 99.5% of people never use.

 

[Wizard69]

Interesting but I'd consider a dial indicator that drops the gears out of mesh upside down as broken. There certainly is an issue with the spring having to counter gravity but even here that shouldn't be a huge problem. The problem here is that over the years I've had a number of occasions to use a gage upside down so to speak, especially in the context of lining up motors to drive shafts, if the gage lost functionality and position every time around the shaft it would be useless.

The more I think about this the more I have to call BS on this. I could see where maybe some gage designs aren't suitable but there are far to many uses where you need to do 360° horizontally. If the gage can't handle that it isn't suitable for the task.

 

[digiex-chris]

I stand corrected! It's not a problem with dial test indicators, they should work upside down. The problem is with dial (plunger style) indicators with the plunger up. They won't necessarily return to zero. My appologies, my original post is wrong. I corrected it. Still didn't know that about plunger style indicators either.

There's a spacer missing from my gear train that fell out when I took it apart. Bah.

 

[10K Pete]

I've used both dial and back-plunger indicators for decades in all positions
with perfect function. Now, if the return spring was 'bad' then I could see
and issue, but otherwise.....!!!

Pete

 

[digiex-chris]

Remember, this is for dial indicators, not dial test indicators. I made a mistake in my first post but I'm unable to edit the title for some reason. Something like this:

I didn't believe it at first either even though I trust Long Island Indicator, so I went looking for manufacturer documentation. Looks like it's not every DI for mitutoyo's digital line, but at least 6 of them have springs available for upside down use.

http://www.mitutoyo.com/wp-content/uploads/2012/09/F-US-1002.pdf

02ACA571, 02ACA573: Optional spring required for upside down use

There's a few more instances of that in that document if you search for the word "upside down". I don't know if most require it and it's just that springs aren't made for the lower cost ones, or if only 6 of them require them.

 

[Charles Lamont]

this is for dial indicators, not dial test indicators.

What is the difference?

 

[digiex-chris]

This type of indicator,

Are susceptible because they're a relatively large mass suspended from a spring. In order to keep reading pressures as low as possible it necessarily can't work the same way the other way around. I suspect it's not a black and white thing, rather it may be a very slight reliability of the first few thou of travel (maybe floating in the rack backlash?), but doesn't affect any measurement off of zero or something like that. I could see it mattering less and less as the travel moves towards the extreme because more spring preload is in play at that point. I've certainly never tried to measure anything within the first .100" or so of a dial indicator, I've always wound it in a bit.

This type,

are not because they're a very small spring that goes through a very large gear reduction. The mass of the tip in any position gone through that gear train is inconsequential to the 0.25N force requirement.

Or that's my take on it anyway. Not an issue for most, and only an issue at the limits of tolerance for the indicators? Maybe only a metrology lab would see an issue.

 

[purpleknif]

Really ? What a bunch of hooey !

 

[Herbiev]

Down here in Oz they only work upside down;D

 

[digiex-chris]

I'm really hoping someone would provide supporting data or documentation from opposing point of views. I'd love to solidify this, but there isn't much here other than experience to the contrary, which I'm not discounting but like a good scientist, I can't confirm or inspect the results by duplication. Admittedly, I'm not finding much to confirm this problem, but I suspect there's some sales pitches involved in that. I'm open to having my beliefs changed back, but the only solid info I'm getting is from Long Island and manufacturer catalogs. If Long Island's position isn't trustworthy, I'd love to know that too. C'mon, I'm craving info!

If it's not interesting I'll just test my own indicators and delete the thread, sorry for bothering you all. Actually I'll test my indicators regardless. Maybe we should all test ours? That'll be interesting, a bunch of different brands and models with the plunger pointed towards the sky and slowly release pressure on the plunger...unfortunately I can't provide results from any high end brands myself but I can provide some tests with two new low cost ones.

Could a mod please edit the thread title and remove the word "test"?

 

[digiex-chris]

Down here in Oz they only work upside down;D

relative to gravity

 

[Charles Lamont]

So, as I suspected, we are comparing lever-type dial (test) indicators with plunger-type dial (test) indicators.

I don't recall having occasion to to use a plunger type indicator upside down, but I am pretty sure my long-travel Mercer gauge would be up to the challenge, as would my cheap East European one, come to that.

 

[digiex-chris]

So, as I suspected, we are comparing lever-type dial (test) indicators with plunger-type dial (test) indicators.

I don't recall having occasion to to use a plunger type indicator upside down, but I am pretty sure my long-travel Mercer gauge would be up to the challenge, as would my cheap East European one, come to that.

I suspected the same, that both of my indicators wouldn't have had a problem, until finding this out. I just finished testing mine.

They're both cheap. Sub-$40. Unfortunately I spent all my money on test indicators, and I only have cheap dial indicators. The results surprised me though. The Shars indicator is brand new, taken out of the box 2 days ago. The Power Fist is several years old, well used, been taken apart, cleaned, and lubed several times.

I did 10 tests per position per indicator, releasing the plunger from about 0.100" back to zero 0.005" per second as close as I could by hand. Here are the images from the most common reading out of each set.

Shars first.

Vertical. Repeated perfectly and solidly.


Left and right. Repeated perfectly, but with less force to make it move. Took enough force that I'm not worried about that repeating at all.




Upside down. Note this is the most common repeat. It once at 0.087, once at 0.082 and once at 0.053, once at 0.055, and 4 out of 10 times within a few thousandths of 0.020. Twice it came right back to zero. This is the most common reading, at 0.020. It took significantly less pressure to depress the plunger in this position.



Here's the powerfist.

Vertical, horizontal. Same kind of solid repetition as the shars, but seems to be smoother on the horizontal than the Shars. There's an additional effect shown by this indicator that didn't happen with the Shars. On rotating to another position, the zero point shifted by 0.002". I re-zeroed in order to test each position.



Upside down. Half of the tests it returned to zero. The other half of the tests showed off by approximately 0.0005". The pressure to move the tip is similar to the Shars, making gravity almost perfectly equaling spring pressure.


I'm surprised that the new one was worse than the old one. perhaps because I've been in the old one taking care of it and it may have had time to wear the rack or gear train in.

So maintenance or wear may be factors. In any case, gravity is certainly a factor. I wish I had the equipment to measure the force required. I would not depend on either of these indicators upside down but I feel confident in them sideways as long as the powerfist is not changing position relative to gravity throughout the measurement.

Anyone feel up to testing a new brand name vs an old brand name?

 

[digiex-chris]

I also cannot make any of these effects happen with my Starret Last Word DTI, my Brown and Sharp plunger back DTI, my Tesatest 0.0001" DTI. My cheap chinese DTI also does not do any of these effects, seems unaffected by position. I didn't test my Compac 244A because that's known broken. Missing a spacer to make the gear train come out of mesh.

 

[poway_bob]

Hi,
Seems like you could put a small washer under the removable tip and add a light spring on the stem.

Bob

 

[digiex-chris]

Yeah that's what mitutoyo seems to recommend, they spec a helper spring for upside down use.

 

[RichD]

I use my plunger type upside down often to track my Z axis on my X3 Mill head. I'll have to watch out for that.
Rich

 

[Charles Lamont]

I spent all my money on test indicators, and I only have cheap dial indicators.

I still don't understand your use of these terms. As far as I know the terms are interchangeable. All are equally "dial indicators" or "dial test indicators", whether they are lever or plunger type.

 

[digiex-chris]

it's a common problem on forums everywhere. They're called different things in different shops on the same street nevermind different countries. There doesn't seem to be one clear word defining each type. The internals are definitely different though. When I'm buying online I most often see types listed into Dial Indicator and Dial Test Indicator categories, with these being in the first

and these being in the last

so that's how I tend to refer to them.

Long Island Indicator seems to use dial indicator vs test indicator. Might be suitable since the test indicators really are only good for comparative measurements whereas the type I tested above are useful for absolute measurement.

 

[Wizard69]

Hi Chris;

Please don't delete the thread as it brings up important information that could save somebody grief down the road. Learning something new every day is important and in this case if what we are learning isn't settled at least the thread raises awareness.

I'm really hoping someone would provide supporting data or documentation from opposing point of views. I'd love to solidify this, but there isn't much here other than experience to the contrary, which I'm not discounting but like a good scientist, I can't confirm or inspect the results by duplication.

It may very well be the case that what happens varies with the manufacture and the specific gage in question. Effectively what you see depends upon the spring chosen for gage and probably tolerance in the spring rate. I could see you getting different results depending upon how far the probe is pushed into the gage.

Admittedly, I'm not finding much to confirm this problem, but I suspect there's some sales pitches involved in that. I'm open to having my beliefs changed back, but the only solid info I'm getting is from Long Island and manufacturer catalogs. If Long Island's position isn't trustworthy, I'd love to know that too. C'mon, I'm craving info!

There are actually different issues here. You mention that one gage you have disengages a gear when turned upside down, I would consider that gage broken. It certainly would be unreliable even in the normal position.

At work we have test Gage's with springs removed thus relying upon gravity. This for materials sensitive to pressure. In my mind the whole reason to have a spring in a gage is to overcome gravity. Maybe that isn't the way the industry looks at it.

If it's not interesting I'll just test my own indicators and delete the thread, sorry for bothering you all. Actually I'll test my indicators regardless. Maybe we should all test ours? That'll be interesting, a bunch of different brands and models with the plunger pointed towards the sky and slowly release pressure on the plunger...unfortunately I can't provide results from any high end brands myself but I can provide some tests with two new low cost ones.

The Gage's should be in good condition. The other thing that might be interesting to review is how the stroke length capability of the gage impacts the results. I would imagine that a gage with a 1/4" of travel would see dramatically different behavior vs one with 4" of travel.

Could a mod please edit the thread title and remove the word "test"?

The way these Gage's are referred to is a little confused. I'm not sure what the right answer here is.